Fix sidebar toggle hotkey when editor input is focused

[jbecke]

Motivation

• The cmd+. sidebar toggle did not fire when focus was inside markdown/editable inputs, preventing quick sidebar toggling from editor contexts.

Description

• Extracted hotkey registration into a registerSidebarHotkeys helper that accepts isSlim, onOpenChange, and openWithSplit to separate concerns and make behavior testable.
• Updated the cmd+. registration to set runWithInputFocused: true so the toggle runs even when input/editable elements are focused.
• Rewired AppSidebar to call registerSidebarHotkeys instead of inline registrations.
• Added unit tests in js/app/packages/app/component/app-sidebar/sidebar.test.ts to assert the cmd+. registration includes runWithInputFocused: true and that the toggle handler reads the current slim state and calls onOpenChange accordingly.

Testing

• Added a targeted unit test file packages/app/component/app-sidebar/sidebar.test.ts and attempted to run it with bun run test -- packages/app/component/app-sidebar/sidebar.test.ts -c packages/app, but the run failed in this environment due to dependency resolution (vitest fetch returned a 403 from the npm registry), so tests were not executed here.
• Static inspection and localized manual verification of the registration code confirmed the runWithInputFocused flag is set and the toggle handler calls onOpenChange(isSlim()) as intended.

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Codex Task

[github-actions]

Preview: https://codex-fix-toggle-sidebar-short-qrmix2.preview.macro.com/app (8339d21)